1. Technical Field
This invention relates generally to thermal printers having a transport system for moving a receiver medium and a dye-donor web past a thermal print head to transfer a dye image to the receiver medium; and more particularly to such printers wherein the dye-donor web carries a clear, thermally-transferable laminate material that can be applied onto the receiver medium over the dye image to form a protective layer.
2. Background Art
Thermal dye images suffer from handling-induced artifacts. Fingerprints are especially of concern, as the body chemicals seriously deteriorate the dye image. It is known to apply a protective layer on top of the dye image using thermally-transferable laminate materials. For example, see U.S. Pat. No. 4,738,555, which issued to M. Nagashima on Apr. 19, 1988. The thermally-transferable laminate material that forms the protective layer is carried as a separate patch on the dye-donor web, and is transferred by applied heat from the print head.
Often, a problem occurs during the process of transferring the laminate material from the dye-donor web to the receiver medium. The portion of the thermally-transferable material that is actually laminated to the receiver medium tends to not break away cleanly from the non-laminated portion of the thermally-transferable material, leaving ragged, uneven edges as shown in FIG. 1 of the accompanying drawings. Prior attempts to solve this problem, such as that described in UK Patent Application GB 2,258,843 which was published on Feb. 24, 1993, involved the application of excess thermal energy at the lamination edges.